1. Field of the Invention
The present invention relates to a method of manufacturing various kinds of link rods in use for a vehicle suspension or the like.
2. Description of the Related Art
There is publicly known a link rod which has a pipe-shaped arm portion and a bush mounting bracket being friction stir welded to an end of the arm portion. There is also publicly known the art wherein a small diameter portion is provided on a mounting projection integrally formed with a bracket, the small diameter portion is engaged with an end of the arm portion and the end of the arm portion comes into butt contact with the mounting projection so as to be friction stir welded along the butt contact portion. Further, there is publicly known the art wherein a material for the bracket is provided for making a plurality of brackets to be cut at a predetermined width in the longitudinal direction, an end of the arm portion is engaged with height difference with the bracket material to be sub-assembled, the sub-assembled arm portion is arranged in such a manner that the plurality of arm portions are arranged in a horizontal row along the longitudinal direction of the bracket material, the engaged portions with height difference are arranged in the shape of a straight line with respect to each of the arm portions so that fraction agitation joining is carried out at a time along the engaged portions with height difference, and thereafter link rods are formed by cutting the bracket material in a predetermined size of a product in the crossing direction thereof.
Patent reference 1: Japanese patent laid-open publication No. H11-101286
Patent reference 2: Japanese patent laid-open publication No. H11-190375
Patent reference 3: Japanese patent laid-open publication No. H11-099415.
When friction stir welding the bracket to the arm portion with a high degree of reliability, tool traveling surfaces in the vicinity of butt portions between both members must be formed in a plane without height difference because the joining with high reliability can not be obtained when friction stir welding the butt portions with height difference like the above-described prior art. Further, in the case where the friction stir welding is carried out from outside of a pipe member, it is required to keep flush without denting the pipe member by pressing the tool so as to obtain the friction stir welding with high reliability. Although these points can be solved by having the mounting projection of the bracket engaged with the arm portion so as to form a flush butt portion like the above-described prior art, it is required to make the small diameter portion each for one or two brackets with respect to one arm portion and to have it engaged with the arm portion, whereby production efficiency can not be improved.